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DaniilM [7]
3 years ago
9

A 10 kg block is attached to a light cord that is wrapped around the pulley of an electric motor, as shown above. At what rate i

s the motor doing work when it is pulling the block upward with an instantaneous speed of 3 m/s and an upward acceleration of 2 m/s

Physics
1 answer:
guajiro [1.7K]3 years ago
5 0

Answer:

the work done by the motor is 531,45 Joules

Explanation:

Using a sketch of the possible conditions, we need to find the distance that the block was moved, in order to find the work done by the electrical motor.

The sketch could be seen in the attached image.

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A chicken crosses a 7.50 m wide road at a constant speed of 0.367 m/s. How much time does it take to cross (in seconds)?
mars1129 [50]
<h3><u>Answer;</u></h3>

= 20.436 seconds

<h3><u>Explanation;</u></h3>

Speed = Distance × time

Therefore;

Time = Distance/speed

Distance = 7.50 m, speed = 0.367 m/s

Time = 7.50/0.367

         <u>= 20.436 seconds </u>

7 0
3 years ago
Read 2 more answers
2. An athlete of average size is hanging from the end of a 20 m long rope, which has a mass of 4 kg and is attached to a hook in
a_sh-v [17]

Answer:

  t = 0.319 s

Explanation:

With the sudden movement of the athlete a pulse is formed that takes time to move along the rope, the speed of the rope is given by

             v = √T/λ

Linear density is

           λ = m / L

           λ = 4/20

           λ = 0.2 kg / m

The tension in the rope is equal to the athlete's weight, suppose it has a mass of m = 80 kg

           T = W = mg

           T = 80 9.8

           T = 784 N

The pulse rate is

          v = √(784 / 0.2)

          v = 62.6 m / s

The time it takes to reach the hook can be searched with kinematics

          v = x / t

          t = x / v

          t = 20 / 62.6

          t = 0.319 s

7 0
3 years ago
Which set of items listed can be arranged to transform electrical energy into mechanical energy?
valentinak56 [21]

Answer:

c

Explanation:

battery, wire, iron

5 0
3 years ago
Firemen are shooting a stream of water at a burning building. A high-pressure hose shoots out the water with a speed of 26.0 m/s
alekssr [168]

Answer:

a) θ = 58.3º

b) vfh = 13.7 m/s

c) g = -9.8 m/s2

d) h = 22.2 m

e) vfb = 15.5 m/s

Explanation:

a)

  • Assuming that gravity is the only influence that causes an acceleration to the water, due to it is always downward, since both directions are independent each other, in the horizontal direction, the water moves at a constant speed.
  • Since the velocity vector has a magnitude of 26.0 m/s, we can find its horizontal component as follows:
  • vₓ₀ = v * cos θ (1)
  • where θ is the angle between the water and the horizontal axis (which we define as the x-axis, being positive to the right).
  • Applying the definition of average velocity, taking the end of the hose like the origin, and making t₀ = 0, we can write the following expression:

        x_{f} = v_{ox} * t = v_{o} * cos \theta * t  (2)

  • Replacing by the givens of xf = 41.0m, t = 3.00 s, and v=26.0 m/s, we can solve for the angle of elevation θ, as follows:

        cos \theta = \frac{x_{f} }{v*t} = \frac{41.0m}{26.0m/s*3.00s} = 0.526 (3)

  • ⇒θ = cos⁻¹ (0.526) = 58.3º (4)

b)

  • At the highest point in its trajectory, just before starting to fall, the vertical component of the velocity is just zero.
  • Since the horizontal component keeps constant during all the journey, we can conclude that the speed at this point is just v₀ₓ, that we can find easily from (1) replacing by the values of v and cos θ, as follows:
  • vₓ₀ = v * cos θ = 26.0 m/s * 0.526 = 13.7 m/s. (5)

c)

  • At any point in the trajectory, the only acceleration present is due to the action of gravity, which accepted value is -9.8 m/s2 (taking the upward direction on the vertical y-axis as positive)

d)

  • Since we know the time when the water strikes the building, it will be the same for the vertical movement, so, we can use the kinematic equation for vertical displacement, as follows:

       \Delta y = v_{oy} * t - \frac{1}{2} *g*t^{2} (6)

  • Our only unknown remains v₀y, which can be obtained in the same way than the horizontal component:
  • v₀y = v * sin θ = 26.0 m/s * 0.85 = 22.1 m/s (7)
  • Replacing (7) in (6), we get:

       \Delta y = 22.1 m/s* 3.0s - \frac{1}{2} *9.8m/s2*(3.00s)^{2} = 22.2 m (8)

e)

  • When the water hits the building the velocity vector, has two components, the horizontal vₓ and the vertical vy.
  • The horizontal component, since it keeps constant, is just v₀x:
  • v₀ₓ = 13.7 m/s
  • The vertical component can be found applying the definition of acceleration (g in this case), solving for the final velocity, as follows:

       v_{fy} = v_{oy} - g*t  (9)

  • Replacing by the time t (a given), g, and  v₀y from (7), we can solve (9) as follows:

       v_{fy} = 22.1 m/s - 9.8m/s2*3.00s = -7.3 m/s  (10)

  • Since we know the values of both components (perpendicular each other), we can find the magnitude of the velocity vector (the speed, i.e. how fast is it moving), applying the Pythagorean Theorem to v₀ₓ and v₀y, as follows:

       v_{f} = \sqrt{(13.7m/s)^{2} +(-7.3m/s)^{2}} = 15.5 m/s (11)

3 0
3 years ago
Help asap!
patriot [66]

Answer:

220 V

Explanation:

r_{1} = 20 ohm\\r_{2} = 30ohm\\r_{3} = 60ohm

As the resistors are connected in series,

R_{eq} = r_{1} +r_{2} +r_{3}

= 20 + 30 + 60

= 110 ohms

V = IR

= 2 * 110

= 220 V

Hope it helps

7 0
3 years ago
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